Sexual reproduction in diploid eukaryotes involves formation of haploid gametes through a specialized cell division known as meiosis. Fusion of two haploid gametes at fertilization recreates diploidy in the next generation. Accurate segregation of chromosomes during meiosis is the central event of sexual reproduction;errors in chromosome segregation result in aneuploid gametes (those with an incorrect chromosome complement). Errors during meiosis are common in humans, and result in fertility issues and birth defects. Thus, a deeper understanding of this process is of clear relevance to human health. In most eukaryotes, including humans, successful formation of haploid gametes involves completion of a choreographed series of events involving pairing of and genetic exchange between homologous chromosome pairs in germ cells undergoing meiosis. This process is conserved among eukaryotes. Our long-term goal is an understanding of the means through which eukaryotes carry out the processes of gametogenesis and meiosis, with a particular emphasis on the behavior of chromosomes during meiosis. The experiments described herein exploit the model system Caenorhabditis elegans, and are designed to identify novel chromatin-associated proteins involved in meiosis and gametogenesis. Proteomics is the simultaneous study of all proteins present in a given tissue at a given time. We propose to identify candidate proteins involved in meiosis through proteomic analysis of germline chromatin. Candidate proteins thus identified will be subjected to bioinformatic and functional analyses, to determine what role(s) they play in meiosis and/or gametogenesis. 1) By comparing proteins present in chromatin-enriched extracts of normal worms with those present in chromatin-enriched extracts from worms lacking normal gonads (and thus germlines), we will identify proteins whose abundance shows a positive correlation with germline chromatin. Identified proteins represent candidates for involvement in meiosis/gametogenesis. 2) Proteins identified in Aim 1 may play roles in meiosis/ gametogenesis. Candidate proteins will be subjected to bioinformatic analyses (expression data;homology comparisons;known mutant/RNAi phenotypes) and phenotypic analyses (resulting from RNAi of candidate gene or deletion of candidate gene). In combination, these approaches will allow determination of the role, if any, played by candidate proteins in meiosis and gametogenesis. Completion of these experiments will identify proteins involved in the conserved processes of meiosis and gametogenesis, and will provide insights into the means through which this important process is carried out. In turn, this may inform diagnosis or treatment of human reproductive defects. Errors occurring during the production of gametes (sperm and/or eggs) are a major cause of human infertility and birth defects. The basic process through which gametes are produced is similar among all animals;here, we propose to use the nematode worm C. elegans to identify proteins involved in gamete production. Information gained from these studies may help with diagnosis and/or treatment of human reproductive problems.